The GSM mobile phones have a higher market share because of its popularization and low cost. The cost of a GSM mobile phone mainly depends on the radio frequency transceiving chip, the Power Amplifier (PA) and the antenna switch. Presently, the common low-end mobile phones are almost GSM double-frequency mobile phones, as the design of GSM four-frequency mobile phones causes higher cost. A GSM four-frequency mobile phone refers to a mobile phone that supports four frequency bands, including the 850 Mhz frequency band, the 900 Mhz frequency band, the 1800 Mhz frequency band and the 1900 Mhz frequency band.
FIG. 1 shows a hardware architecture diagram for transceiving of the GSM four-frequency mobile phones, comprising an antenna switch 101, a filter 102, a PA 104 and a radio frequency transceiving chip 103, wherein the antenna switch 101 transmits the signals received from the antenna to the filter 102 for filtration, and then transmits the filtered signals to the radio frequency transceiving chip 103; the radio frequency transceiving chip 103 transmits the signals to be transmitted to the PA 104 for power amplification, and then the power amplified signals are transmitted to the antenna switch 101, and then transmitted through the antenna; wherein, the antenna switch 101 is connected with the filter 102 through four signal lines, and the filter 102 comprises a GSM850 filter, a GSM900 filter, a GSM1800 filter and a GSM1900 filter; the filter 102 realizes the filtration for the signals of the different frequency bands via a resonator therein, the signals which have the same frequency band as the resonant frequency of the resonator are pass band signals that can pass the filter, and the signals outside the resonant frequency are stop band signals that can be removed by the filter. Meanwhile, in order to inhibit the signal errors effectively, the output signals of the filter 102 output differential signals; the radio frequency transceiving chip 103 comprises four receivers and four transmitters, wherein the four receivers are respectively used to receive differential signals transmitted by the four filters, and power amplify the received differential signals; the four transmitters are respectively used to convert the respectively received signals to radio frequency signals, which are then transmitted to the PA 104; the PA 104 is connected with the antenna switch 101 through the four signal lines transmitting the four frequency bands; the four-frequency antenna switch is costly, and the antenna switch is connected with the filter 102 and the PA 104 through eight lines, and three logic control lines are required to control the state of the switch; meanwhile, the filter 102 is connected with the radio frequency transceiving chip 103 through four groups of differential signal lines, and the PA 104 is connected with the radio frequency transceiving chip 103 through four lines; in connection with the higher cost, the lines are also complicated, which causes the layout of those lines to be difficult.
Presently, with the increased amplification capacity of the receiver and the PA, the GSM four-frequency transceiving hardware architecture shown in FIG. 2 is generally used. Different from FIG. 1, GSM850 filter and GSM900 filter are connected with the receiver of the radio frequency transceiving chip by sharing a group of differential signal lines; GSM1800 and GSM1900 are connected with the receiver of the radio frequency transceiving chip by sharing a group of differential signal lines; GSM850 frequency band and GSM900 frequency band share a transmitter for transmitting signals; GSM1800 frequency band and GSM1900 frequency band share a transmitter for transmitting signals; PA is connected with the antenna switch through two signal lines, wherein one line is used to transmit signals of GSM850 frequency band and GSM900 frequency band, and the other line is used to transmit signals of GSM1800 frequency band and GSM1900 frequency band. In this way, the transmitting lines and the receiving lines are simplified, and two transmitters and two receivers are saved. However, the antenna switch is connected with the filter and the PA through six signal lines, and three logic control lines are still required to control the antenna switch, the cost of the four-frequency antenna switch is not reduced.